US4703296A - Thermal reed switch assembly - Google Patents

Thermal reed switch assembly Download PDF

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Publication number
US4703296A
US4703296A US06/826,634 US82663486A US4703296A US 4703296 A US4703296 A US 4703296A US 82663486 A US82663486 A US 82663486A US 4703296 A US4703296 A US 4703296A
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Prior art keywords
reed switch
thermal
magnetic members
thermal magnetic
switch assembly
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US06/826,634
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English (en)
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Tomio Katoh
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TDK Corp
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TDK Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/02—Details
    • H01H37/32—Thermally-sensitive members
    • H01H37/58—Thermally-sensitive members actuated due to thermally controlled change of magnetic permeability
    • H01H37/585—Thermally-sensitive members actuated due to thermally controlled change of magnetic permeability the switch being of the reed switch type

Definitions

  • the present invention relates to a thermal reed switch assembly which is capable of performing a bandless operation with adjustment of an operating temperature and achieving a widened difference range between its operating temperature and reset temperature by selectively establishing such two temperatures at desired points respectively.
  • thermal reed switch assembly of bandless operation type combined with a thermal magnetic member and a permanent magnet so as to be turned off (or on) above a certain temperature or turned on (or off) below such temperature
  • thermal magnetic member of the material composition that indicates required characteristic change relative to the operating temperature
  • a plurality of thermal magnetic members of different material composition need to be prepared for individual operating temperatures. Therefore a problem has been existent heretofore that unless various kinds of thermal magnetic members are prepared, it is impossible to produce a satisfactory thermal reed switch assembly which functions at any desired operating temperature.
  • the reset temperature is determined at a given lower point (e.g. lower by 3°-4° C.), whereby it is rendered impossible to select desired temperatures respectively or to increase the temperature difference therebetween to a desired range.
  • FIG. 9 (a) is a sectional view of a conventional break type reed switch assembly (whose contacts are disconnected above its operating temperature), and FIG. 9 (b) graphically shows the principle of operation of the thermal reed switch with the relationship between the temperature and the magnetic flux which flows in the contact region of the switch (where the flux flowing rightward in the drawing is positive).
  • the reed switch 6 has a contact region 5 in the axial center of an elongated glass receptacle, and two ferromagnetic reed pieces 3 and 4 supported in the receptacle extend axially from the contact region 5 in mutually opposite directions.
  • Designated at 1a and 1b are permanent magnets whose magnetic transition point (Curie point) is sufficiently higher than the operating temperature, and a thermal magnetic member 2 having a Curie point equivalent to the operating temperature is disposed opposite to the contact region 5.
  • the permanent magnets 1a and 1b are attached firmly to the reed switch 6 while being opposed to the reed pieces 3 and 4 in such a manner that the direction of magnetization thereof becomes coincident with the axial direction of the reed switch. Assume now that a temperature rise occurs in the above arrangement.
  • the thermal magnetic member 2 Since the thermal magnetic member 2 remains ferromagnetic under its Curie point, the magnetic flux flowing from the magnet 1b to the magnet 1a mostly passes through the magnetic member and thereby forms a magnetic circuit which extends by way of the reed pieces 3 and 4, so that the magnetic flux flowing in the contact region 5 provides a great force of attraction sufficient to retain the contacts at the attracted positions thereof against the elasticity of the reed pieces 3 and 4.
  • Such magnetic flux flowing in the contact region 5 gradually decreases in accordance with temperature rise, as represented by the curve shown in FIG. 9 (b). That is, the saturation flux density of the thermal magnetic member 2 is reduced and consequently the magnetic flux flowing therein leaks out to the contact region 5.
  • the leakage flux is directionally reverse to the magnetic flux passing through the contact region 5 and, as a result of the mutual cancellation thereof, the flux flowing in the contact region 5 decreases.
  • the temperature (represented by OT) at this moment is the operating temperature.
  • the magnetic flux fails to provide, even after arrival of the temperature at OT, a great force of attraction sufficient to overcome the elasticity of the reed pieces 3 and 4.
  • RT reset temperature
  • the present invention has been accomplished in view of the circumstances mentioned above. And its object is to provide an improved bandless type thermal reed switch assembly wherein a wide temperature hysteresis range is attainable by establishing both an operating temperature and a reset temperature at desired points respectively, and fine adjustment is executable as well with another advantage of ensuring high operational reliability.
  • the feature of the present invention resides in a novel structure wherein at least two permanent magnets are disposed in the peripheral vicinities of the contact region of a reed switch having two magnetic reed pieces, in such a manner that the poles of the permanent magnets are directionally coincident with the axes of the reed pieces, and at least two thermal magnetic members having mutually different magnetic transition points are so disposed as to sandwich the reed switch therebetween in the direction intersecting the axis of the reed switch.
  • FIG. 1 (a) is a perspective view of an exemplary embodiment according to the present invention
  • FIG. 1 (b) graphically shows the magnetic flux-to-temperature characteristic for explaining the principle of operation
  • FIGS. 2 (a) and 2 (b) are perspective views illustrating exemplary shapes of thermal magnetic members employed in the embodiment of FIG. 1 (a);
  • FIGS. 3 and 4 are perspective views illustrating other exemplary shapes of thermal magnetic members
  • FIG. 5 graphically shows the magnetic flux-to-temperature characteristic for explaining the operation of a modification
  • FIGS. 6 and 7 are perspective views of further exemplary embodiments according to the invention.
  • FIG. 8 graphically shows the magnetic flux-to-temperature characteristic of the assemblies illustrated in FIGS. 6 and 7;
  • FIG. 9 (a) is a perspective view of a conventional assembly.
  • FIG. 9 (b) graphically shows the magnetic flux-to-temperature characteristic of the assembly illustrated in FIG. 9 (a).
  • FIG. 1 (a) is a perspective view of an exemplary reed switch assembly embodying the invention
  • FIG. 1 (b) graphically shows magnetic flux-to-temperature characteristic curves for explaining the principle of operation.
  • aforesaid magnetic member 2 of FIG. 9 (a) is replaced with two semicylindrical thermal magnetic members 10a and 10b which have mutually different Curie points and butt against each other to be cylindrical while sandwiching the reed switch 6 therebetween.
  • a curve X represents the characteristic of the thermal reed switch obtained when one thermal magnetic member 10a is shaped into a ring and is used solely
  • a curve Y represents the characteristic obtained when another thermal magnetic member 10b is used solely.
  • a curve Z plotted by a broken line between the foregoing two curves represents the characteristic achieved by the present invention, wherein the operating temperature OT is within an intermediate region of OT1-OT2 and at a position closer to OT2, and the reset temperature RT is within an intermediate region of RT1-RT2 and at a position closer to RT1, so that the difference (temperature hysteresis) between the operating temperature and the reset temperature can be established to have a wide range.
  • thermal magnetic member 10a of FIG. 2 (a) which is semicylindrical in cross section and has an inner circumference 10a 1 substantially equal to the outer semicircle of the reed switch 6, and another semicylindrical thermal magnetic member 10b equal in shape thereto is combined with the member 10a to constitute a cylindrical unit of FIG. 2 (b).
  • one thermal magnetic member 10a is shaped to be arcuate in cross section while another thermal magnetic member 10b is shaped into a U in such a manner as to support the remaining cylinder portion, and the sectional area ratio of the two members may be changed.
  • the sectional area ratio of the two thermal magnetic members 10a and 10b may be changed by increasing the inner diameter (thickness) 10a 1 of one member.
  • FIG. 5 graphically shows the characteristic achieved in the case where the sectional area ratio of the two thermal magnetic members 10a and 10b is changed and the temperature hysteresis range is widened by selecting the Curie points thereof to be considerably different from each other.
  • a curve A represents the result obtained by decreasing the inner diameter of the cylindrical thermal magnetic member (i.e. by increasing the cross-sectional area). The curve A shifts upward as the sectional area becomes further greater.
  • a curve B represents the result obtained by increasing the inner diameter of the cylindrical thermal magnetic member (i.e. by decreasing the sectional area) contrary to the preceding example. The curve B shifts downward with a further decrease of the cross-sectional area.
  • another curve C plotted by a broken line represents the result obtained by increasing the inner diameter of merely one thermal magnetic member (10a in FIG. 4) having a higher Curie point, denoting that both the operating temperature and the reset temperature are adjustable.
  • the temperature hysteresis range can be widened and high operational reliability is ensured by the following reasons.
  • the magnetic flux passing through one thermal magnetic member of a higher Curie point is maintained even when another thermal magnetic member of a lower Curie point loses its magnetism, thereby retaining the switch in its on-state. Consequently its off-action is determined by the higher Curie point.
  • the passing magnetic flux is thereby restricted to retain the off-state with certainty if the temperature falls below the higher Curie point during the downward fluctuation thereof. And upon arrival of the temperature at the lower Curie point, the magnetic flux is suddenly increased to immediately turn on the switch. Accordingly, the on-off action can be performed with certainty.
  • both the operating temperature and the reset temperature are selectively changeable by varying the sectional area ratio of the thermal magnetic members as mentioned above, hence facilitating fine adjustment of the characteristic.
  • the present invention is applicable also to a make type as shown in FIGS. 6 and 7.
  • two spacers 11 are positioned on the two sides of thermal magnetic members to form gaps.
  • two pairs of thermal magnetic members are disposed with one spacer 11 inserted therebetween to form a gap.
  • the magnetic flux-to-temperature characteristic curve is such as plotted in the graph of FIG. 8.
  • each thermal magnetic member need not exactly be cylindrical or the like, and it may be prismatic or elliptic as well.
  • the essential requisite resides merely in the point that such magnetic members are in the shape obtained by dividing a hollow post longitudinally.
  • the present invention realizes an improved thermal reed switch assembly in which a wide temperature hysteresis range can be attained with another advantage of ensuring high operational reliability.
  • the use of a single thermal reed switch assembly of the present invention is sufficient to achieve the purpose in an exemplary case of employing the invention in an antifreezing mechanism of a heat pump type air conditioner or the like, as compared with a conventional application where signals for starting a defrost mode (at -3° C.) and ending it (at 14° C.) are obtained from individual sensors separately.

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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Switches That Are Operated By Magnetic Or Electric Fields (AREA)
  • Thermally Actuated Switches (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)
US06/826,634 1985-02-07 1986-02-06 Thermal reed switch assembly Expired - Lifetime US4703296A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP1985016074U JPH0312188Y2 (ja) 1985-02-07 1985-02-07
JP60-16074[U] 1985-02-07

Publications (1)

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US4703296A true US4703296A (en) 1987-10-27

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US06/826,634 Expired - Lifetime US4703296A (en) 1985-02-07 1986-02-06 Thermal reed switch assembly

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US (1) US4703296A (ja)
JP (1) JPH0312188Y2 (ja)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5512732A (en) * 1990-09-20 1996-04-30 Thermon Manufacturing Company Switch controlled, zone-type heating cable and method
US10422704B2 (en) 2014-12-02 2019-09-24 3M Innovative Properties Company Magnetic based temperature sensing for electrical transmission line

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2877315A (en) * 1956-06-19 1959-03-10 Bell Telephone Labor Inc Electromagnetic relay
US3663913A (en) * 1967-12-22 1972-05-16 Tohoku Metal Ind Ltd Core coil having a improved temperature characteristic
US3895328A (en) * 1972-11-30 1975-07-15 Tohoku Metal Ind Ltd Thermo-magnetically operated switches
US3947794A (en) * 1972-12-11 1976-03-30 U.S. Philips Corporation Magnetic core assemblies with adjustable reluctance as a function of temperature
JPS5535425A (en) * 1978-09-05 1980-03-12 Tohoku Metal Ind Ltd Temperature sensing reed switch
US4320370A (en) * 1977-11-07 1982-03-16 Tdk Electronics Company, Ltd. Thermo-sensitive reed switch
US4325042A (en) * 1979-05-14 1982-04-13 Tohoku Metal Industries, Ltd. Thermo-magnetically operated switches having two different operating temperatures
US4389628A (en) * 1980-06-02 1983-06-21 Tohoku Metal Industries, Ltd. Thermo-magnetically operated switches having two different operating temperatures
US4509029A (en) * 1984-03-09 1985-04-02 Midwest Components, Inc. Thermally actuated switch

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2877315A (en) * 1956-06-19 1959-03-10 Bell Telephone Labor Inc Electromagnetic relay
US3663913A (en) * 1967-12-22 1972-05-16 Tohoku Metal Ind Ltd Core coil having a improved temperature characteristic
US3895328A (en) * 1972-11-30 1975-07-15 Tohoku Metal Ind Ltd Thermo-magnetically operated switches
US3947794A (en) * 1972-12-11 1976-03-30 U.S. Philips Corporation Magnetic core assemblies with adjustable reluctance as a function of temperature
US4320370A (en) * 1977-11-07 1982-03-16 Tdk Electronics Company, Ltd. Thermo-sensitive reed switch
JPS5535425A (en) * 1978-09-05 1980-03-12 Tohoku Metal Ind Ltd Temperature sensing reed switch
US4325042A (en) * 1979-05-14 1982-04-13 Tohoku Metal Industries, Ltd. Thermo-magnetically operated switches having two different operating temperatures
US4389628A (en) * 1980-06-02 1983-06-21 Tohoku Metal Industries, Ltd. Thermo-magnetically operated switches having two different operating temperatures
US4509029A (en) * 1984-03-09 1985-04-02 Midwest Components, Inc. Thermally actuated switch

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5512732A (en) * 1990-09-20 1996-04-30 Thermon Manufacturing Company Switch controlled, zone-type heating cable and method
US10422704B2 (en) 2014-12-02 2019-09-24 3M Innovative Properties Company Magnetic based temperature sensing for electrical transmission line

Also Published As

Publication number Publication date
JPS61132664U (ja) 1986-08-19
JPH0312188Y2 (ja) 1991-03-22

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